A known method for determining the location of impacts on an object is based on acoustic image generation. According to this method, a surface of the object is subdivided in M areas, for example like an array, and N acoustic sensors are fixed for example on the surface. Each acoustic sensor i is arranged to receive an acoustic signal generated from an impact on the object surface and to transmit a sensed signal si(t) to a processing unit.
For each area k of the array, the sensed signals si(t) are delayed of a time delay compensation τik and summed forming Pk. This time delay compensation τik is a determined value based on the respective locations of the area k and of the sensor i. As shown in FIG. 1a, if the sensed signals si(t) are correctly delayed, i.e. if the impact was generated in the area k, the delayed signals are in phase and Pk has an impulse shape. As opposed to and as shown in FIG. 1b, if the sensed signals si(t) are not correctly delayed, i.e. if the impact was not generated in the area k, Pk is wide and his maximal value is low. Thus, for each area k of the array, the Pk maxima are computed, forming thus an acoustic image of the impact. A comparison of the Pk permits then to localize an impact generated on the surface.
Yet, the time origin in such a method is not correctly determined, leading to synchronization problems in the processing unit. In consequence, failures to determine the location of impacts occur. Moreover, the accuracy of this method is dependant on the shape and, in particular, the duration of the impact signals. Then, the longer an impact signal lasts, the lower the accuracy is.
An object of the present invention is to provide a method for determining the location of an impact, whose accuracy does not depend on the impact signal waveform.
Another object of the invention is to provide a robust method for determining the location of impacts.